3M Co. wasn’t too pleased when its former law firm, Covington & Burling, began working for Minnesota’s attorney general in a lawsuit against the company. Now the state of Minnesota is fighting 3M’s efforts to get the firm thrown off the case, Reuters reports.

The tech giant claims that Covington was its legal adviser for decades, frequently on environmental matters related to the company’s chemical businesses. But in December 2010, the firm purportedly dropped 3M as a client and signed on to a Minnesota state investigation into water pollution allegedly resulting from 3M’s perfluorochemicals. 3M sued its former counsel for breach of contract and breach of fiduciary duty.

But Covington maintains that it has previously represented the state of Minnesota in environmental cases and that its ex-client "has the situation completely backwards in suggesting that the firm dropped a long-time client to represent the State."

Minnesota Solicitor General Alan Gilbert also questioned the timing of 3M’s motion, saying that it came long after the original complaint, but “shortly after recent incriminating testimony by 3M employees.” Gilbert also told Judge Deborah Hedlund that Covington & Burling’s disqualification “would severely prejudice the State, and the State may not even be able to continue prosecution of the case.”